Golang Array Quick Notes

An array is a numbered sequence of elements of a specific length. If you need something which can grow and shrink then use slice instead. If you have come from a PHP background, then u can think of it as an indexed array [1, 2, 3] but the type is strict.

//Declaration
var a [5]int

• If the element’s value is not assigned then zero value/default value of the type is used. For int type the zero value is 0. So variable a contains 5 zero in this case

e := [3]bool{true, 1 == 1}
//3rd element is not assigned. So its a zero value(defaults to false for boolean)
fmt.Println(e) //output: true, true, false

• Array length declared inside the square bracket [] is determined during compile time. So you cannot declare like this:

var a[x]int //this is not possible where x is a variable that might   chnage at any time

• arrays are reference type, meaning you can directly change a value like this:

a[1] = 100

• Shorthand Declaration:

a := [4]int{1, 2, 3, 4} //shorthand declaration
fmt.Println(a[0]) //output: 1

• Declaring without specifying the size

abc := [...]int{1, 4, 5, 1, 4, 6}

The three dots … tells the compiler that figure out yourselves the length of this array.
Note: if you omit the three dot then it will turn into a slice which is just like an array but can grow and shrink

• accessing part of array

z := [5]int{61, 62, 33, 14, 45}
//   index: 0   1   2   3   4

Here is the syntax to access elements: (VERY IMPORTANT)

 z[startIndexIncluding : uptoNotIncludingIndex]

• Some Examples

fmt.Println(z[2:4]) //output: [33, 14]
//if we want to access value from index 0 to index 3 then
fmt.Println(z[:3])  //output: 61 62 33
if we want to access from index 1 to end then
fmt.Println(z[1:])  //output: 62 33 14 45

• to find the length

length := len(z)